Cubic–tetragonal phase change of yttria-doped hafnia solid solution: high-resolution X-ray diffraction and Raman scattering

High-resolution synchrotron X-ray powder diffraction and Raman scattering have demonstrated the existence of tetragonal yttria-doped hafnia solid solution with an axial ratio, cf/af, of unity, but having displacements along the cf-axis from the ideal fluorite position in the oxygen sublattice. The values of cf/af ratio in HfO2–X mol%YO1.5 samples (X=13, 14, and 16) are estimated to be unity with the precision of ±0.00003 from the estimated standard deviation of the peak position and less than ±0.001 from the full-width at the half-maximum of the 400f reflection peak. However, the Raman spectra of the samples of X=13, 14, and 16 clearly demonstrate the tetragonal phase.